The Development Of Three Channels HCN Laser Interferometer On EAST

Electron density is one of the important parameters in plasma, and its temporal and spatial distribution is related to the study of various physical phenomena. Far infrared laser interferometer is a standard diagnostic for measuring the electron density profile. Three channels HCN laser interferometer is developed under the operating characteristics on EAST,and five channels DCN laser interferometer is under pre-research. In this M.Sc thesis, principle of laser interferometer and the structure of three channels HCN laser interferometer are presented briefly. The laser structure is optimized by replacing the oil jacket with automated system for changing the length of laser cavity. Gaussian beam transmission in large diameter waveguide is made detailed studies. The material, shape and diameter are decided, and the waveguide and elbow coupling are designed and processed. Lock-in amplifier system for measuring the weak signal is first introduced in the experiment. The three channels HCN laser interferometer has been successfully applied in the EAST experiment.Using single channel HCN laser interferometer, the main plasma density is raised by gas puffing. Comparing the divertor probe date, three different divertor regimes, i.e., low recycling (divertor plasma density is low, temperature is high), high recycling (divertor plasma density is high, temperature is low), and detached divertor plasma (divertor plasma density is low, temperature is low), are first obtained on EAST.Considering the laser divergence angle, HCN laser (337μm) can only be divided into three probe beams in the EAST vertical window, but the DCN laser (195μm) can be divided into five probe beams. Five channels DCN laser interferometer is being pre-study. The DCN laser and optical system has been designed and processed, and the drying system is being developed on EAST.